Method of forming paving compositions



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METHOD OF FORM ING- PAVING COMPOSITIONS. V

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My present invention relates to concrete compositions for pavements, ,sidewalks and the like, which contain a bituminous binder other than the substantially solid bitumen referred to in my Patent No. 1,519,560, granted December 16, 1924:; and m present invention relates more particular y to asphaltic paving compositions contalning, in suitable admixture with diatomaceous earth, such asphaltic materials as are commonly found in California, and other Western States, as also in Central and South American countries, and elsewhere.

It is an object of this invention to provide improved asphaltic paving compositions utilizing naturally fluent asphalts or asphalt fractions, and requiring no use of Trinidad asphalt, 'orother solid asphaltic ingredients and it is a further object of my-invention to provide an improved method of preparing the novel compositions herein described,.or analogous compositions.

As in the case of the prior patent men tioned, ll attribute the meritorious qualities of my novel aving compositions mainly to a skillful and j'ud1cious proportioning and incorporation of diatomaceous earth; and my former opinion in this regard is confirmed by the facility with which composithose described in my mentioned patent may be prepared, even without the use of solid bitumens, provided the constituent materials,-including a'viscous or liquid asphalt, but not necessarily including any crude petroleum distinct therefrom, are treated and associated in substantially the m'anner hereinafter described. a

As heretofore mentioned, I have dis covered that diatomaceous earth, when used in proper proportions, and treated in a manner favorable to the utilization of its natural properties, not only causes apavement containing the same to remain substantially unafi'ected by temperature changes, but also exhibits cementitious properties in the amalgamation of concrete, toughening the pavement and rendering it moreelastic and durable. Depending, however, upon the climate in which the composition is to be used, the diatomaceous earth must be suitably proportioned relatively to the asphaltic material with which it is, in the process herein described, initially associated in a fluent material adapted to be, admixed, while hot, with an aggregate material also Application filed August 17,1925. Serial No. 50,853. Q

preheated; and it is an important feature of the novel process herein described-that the diatomaceous earth is first separately preheated, when used without additions of crude oil such as are mentioned in my patent above referred to, to a temperature far above the boiling point of water,-even such as a temperature in excess of 1200 F, to facilitate the subdivision of the diatomaceous tlti earth and the separation of clay therefrom.

(Ether features and advanta es of my invention, 1n the practice of whic the proport1on of diatomaceous earth may be so varied as to adapt the resultant composition to use either in a tropical or in a cold climate, may be best understood from the following description of an advantageous procedure in the preparation of a pavin composition suitable for use in, for examp e, the climate of southern California:

it may initially preheat a suitable quantity 'of an asphaltic composition, such as a composition showing a penetration of .40 to it {as compared with a penetration of about .35, in the case of Trinidad asphalt-the test here referred to being executed at about 77 F.',-using a No, 2 needle, a weight-of 100 grams, a-period of 5 seconds, and proceeding in accordance with the course ap proved by the American Society for Testing Materials, at its 1916 annual meeting) to a temperature such as 300 to 350 F,

more or less; and into this preheated asphalt I may incorporate (as by mixing the same in an agitator having, for example, a capacity of 50 barrels and for a period such as 1 to 2 hours) from 5% to 35% by weight of 'diatomaceous earth, previously heated to a temperature such as 600 F., more or less.

When the paving composition into which the described mixture is incorporated is to be used in a climate such as that of Los Angeles, California, 10 to 15 pounds of diatomaceous earth may advantageously be thus initially associated with each 85 pounds of preheated asphalt; and after this mixture has been agitated for a, p'eriod sufiicient to render the same substant ally homogeneous,

the temperature being keptabove 300 F., I.

may add 6% to 15% of the same to 85%-94% of a suitable aggregate, as an aggregate containing sharp sand and hardgravel in graduated sizes and suitable proportions,-the dry mixture ofggregate materials having been also brought to a temperature above all before its temperature shall drop below about lon gregate,

' Any temperature between about 15:30, F. and 250 F. is suitable to the rolling and finishing of a pavement containing the described composition,which should, of

course, be laid upon a dry and solid base,

preferably to a thickness not less than 1 inch, the top surface being either finished in a general manner described in my mentioned patent or by the application of a seal coat of hot asphalt uniformly squeegeed over the surface at the rate of from .2 to .3 galpler square yard. After the squeegee coat as been applied, hot screening may be broadcasted over the surface, in the case of rolled until fairly bonded to the road, additional screening being optionally spread and broomedover the surface, during rolling, in sufficient quantity to take up all excessasphalt.

In explanation of my reference to the use of comparatively high temperatures in conditioning the diatomaccous earth, I may mention that temperatures greatly in excess of the boiling point of water are, if at all, used, primarily to facilitate the separation of foreign matter such as clay, presentas an impurity in most commercial diatomaceous earth. Temperatures above 3000 F. must be avoided as tending to break up the diatom skeletal units and temperatures as low as 600 F., or less, may be sufficient in case the heating is done in blower tube, the clay being caught on a screen through which the diatoms'pass. When a rotary fiirnace is used, a satisfactory purification of the diatomaceous earth may be favored by a temperature even above 2000 F. the clay tending to collect at a lower level but being removable by, for example, a tilting of thg furnace. In any case, originally ure or purified diatomaceous earth may e permitted to cool to about the temperature of the hot asphalt before it is admixedtherewith.

Relative proportions of coarse and fine agand the maximum sizes tolerated, may naturally depend upon the thickness of the pavement; and the proportion of diatomaceous earth initially associated with fluent asphalt, after suitable preheating of both of these ingredients, may vary from, for example, I 20% of diatomaceous earth with 80% of asphalt, when my composition a pavement intended for vehicular use, and

is to be used in a torrid climate such as that of the Imperial Valley, California, to proportions such as 5% of diatomaceous earth used with 95% of fluent asphalt, when the composition is to be used in a cooler climate ing suggested as suitable for use in San Francisco, and 10% to 15% being suitable for use in Los Angeles. It "will, however, be understood that all figures given herein are merely illustrative of the principles and practice of my invention, numerous additions and modifications being possible, without the slightest departure from the spirit and scope of my invention, as the same is indicated above and in the following claims.

I claim as my invention:

1. A method of forming paving com y sitions which comprises: separately pre eating naturally fluent asphalt, showing a penetration of about .40 to .75 under conditions which result in a enetration of only about .35 in the case of, 'rinidad asphalt, and diatomaceous earth to temperatures about 300 F., the diatomaceous earth being heated to a higher temperature than the asphalt and incorporated therewith in proportion between 5% and 35%; separately preheating an aggregate mixture to a temperature above 300 F.; and mixing the resultant asphaltie-diatomaceous earth mixture with said aggregate mixture at an elevated temperature.

such as that of Seattle, Washingt0n,-8% be 2. A method of forming paving'com ositions which comprises: separately pre eating naturall fluent asphalt, showing a penetration of a out .40 to .75 under conditions I which result in a penetration of only about .35 in the case of Trinidad asphalt, and diatomaceous earth to temperatures above 300 F., the diatomaceous earth being heated to a higher temperature than the asphalt and incorporated therewith in proportions between 5% and 35%; separately preheating an aggregate mixturev to a temperature above 300 F.; and mixing the resultant asphaltic diatomaceous earth mixture with said aggregate mixture at an elevated temperature, said diatomaceous earth, when contions which comprises: separately preheat- ,taining foreign matter, being first preheated "'to a. temperature between 600 F.. and

atomaceous earth to an elevated tempera- 2 ture, the diatomaceous earth being heated to a higher temperature than the asphalt, the diatomaceous earth and the described naturally fluent asphalt being mixed at an elevated temperature in proportions between 5% of diatoniaceous earth with 95% of asphalt-and 35% of diatomaceous earth "use with 65% of asphalt by weight, separately preheating an aggregate mixture to a temperature above 300 F.; and mixing the resultant asphaltic-diatomaceous earth mixture with said aggregate mixture at an elevated temperature.

4. A method of forming paving com ositions which comprises: separate? pre eating naturally fluent asphalt an'- diatomaoeous earth to temperatures above 300 F., 10

tween 5% and 35%. In testimony whereof, I have hereunto set my hand at Los Angeles, California, this day of August, 1925.

CHARLES SWAN. 

